Image capture device is used to capture images of an object side through a lens and an image sensing element therein; wherein the lens is used to focus the light beam from the object side to the image sensing element. Generally, lens can be divided into fixed lens and zoom lens. Because having variable focal length, the zoom lens has some advantages such as the easy-to-use feature. A good zoom lens is defined to have good image quality at every focal length. Thus, it is quite important for a lens designer to design a zoom lens having good image quality at every focal length.
Currently, many patents about zoom lens have been published or disclosed, such as U.S. Pat. Nos. 8,369,021, 5,481,404, 8,477,427, 4,838,669, 8,654,451, 4,468,097, 5,146,366 and 5,132,848. However, the conventional zoom lens usually uses two or more than four groups of lens set. Specifically, for the zoom lens using two groups of lens set, the resolution optimization may not be achieved simultaneously in all the focal lengths at the wide-angle end, the telephoto end and the middle position; as a result, the resolution in some specific focal lengths must be sacrificed. On the contract, for the zoom lens using four or more groups of lens set, the manufacturing cost is high due to a relatively-complex driving mechanism for driving the four or more groups of lens set is required.